MiR-145 Alleviates Sepsis-Induced Inflammatory Responses and Organ Injury by Targeting ADAM17

Background: Current studies have demonstrated that disintegrin and metalloproteinase 17 (ADAM17) plays a critical role in the pathogenesis of sepsis. MicroRNA (miR)-145 is known to control immune responses as an anti-inflammatory modulatory molecule. However, a fundamental understanding of how miR-145 regulates ADAM17 and, more broadly, sepsis-induced inflammatory response remains unknown. Methods: We used western blotting and quantitative real-time PCR (qRT-PCR) to measure expression levels of ADAM17 and miR-145. Enzyme-linked immunosorbent assays (ELISA) were performed to measure cytokine production. To determine if ADAM17 is a target gene of miR-145, bioinformatics analyses and luciferase reporter assays were conducted. The impacts of ADAM17 and miR-145 on sepsis-induced inflammatory responses were accessed in vitro using human umbilical endothelial cells (HUVECs) treated with lipopolysaccharide (LPS). Sepsis-induced inflammatory response was measured in vivo using a polymicrobial septic mouse model induced by cecal ligation and puncture (CLP) with pre-injection of a miR-145 agomir. Results: In HUVECs treated with LPS, miR-145 expression was downregulated and miR-145 negatively regulated ADAM17 expression through direct binding to the ADAM17 transcript 3′-UTR. MiR-145 overexpression markedly reduced LPS-induced inflammatory cytokine production by targeting ADAM17 in HUVECs. In comparison to CLP-induced septic mice treated with a control agomir, treatment with a miR-145 agomir significantly reduced the expression of ADAM17, numerous downstream cytokines such as IL-6, TNF-α, IL-1β and MCP-1, and the endothelial injury factors ICAM-1, VCAM-1. The miR-145 agomir also alleviated acute lung and kidney injury and improved the survival rate of septic mice. Conclusions: This study showed that miR-145, by specifically targeting ADAM17, negatively regulates sepsis-induced inflammatory responses and vascular endothelial injury, and ultimately improved organ injury and survival during sepsis. The underlying mechanism for the regulation of ADAM17 expression by miR-145 and sepsis-induced inflammatory reactions may offer sepsis patients a novel therapeutic option.